The meningitis vaccine NeisVac-C is a group C meningococcal polysaccharide conjugated to tetanus toxoid. The polysaccharide is recovered from the Neisseria meningitidis cell capsule and is purified by base treatment with subsequent diafiltration to remove hydrolyzed cell impurities. Purified polysaccharide is clear to slightly cloudy. A recent group of successive lots contained large amounts of precipitate that had not been observed in 10 previous years of commercial manufacturing. The precipitate was mostly composed of the sodium salt of palmitic acid (C16:0) with lesser amounts of palmitoleic (C16:1), oleic (C18:1), stearic (C18:0) and myristic (C14:0) sodium salts. The elevated fatty acid levels that formed the precipitate were linked to a damaged pump used during harvest. Replacement of the damaged pump corrected the issue and >15 lots have since been produced without precipitation.

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NeisVac-C is a vaccine that prevents the invasive disease caused by Neisseria meningitidis serogroup C. The active ingredient is a polysaccharide–protein conjugate. Each dose contains 10 µg of de-O-acetylated group C meningococcal polysaccharide (GCMP) conjugated to 10-20 µg of tetanus toxoid protein and adsorbed onto 0.5 mg of aluminum as aluminum hydroxide in saline.

Figure 1: Visible precipitation during GCMP purification.

The GCMP is isolated from the culture medium of Neisseria meningitidis by microfiltration. The microfiltration permeate is concentrated and diafiltered to remove small soluble fermentation components. The major purification step is a saponification reaction in which the GCMP is refluxed with high concentrations of base for several hours. After diafiltration, the mixture typically appears clear to slightly cloudy. A recent cohort of successive GCMP lots contained a precipitate that had not previously occurred in ten years of commercial manufacturing (see Figure 1). This article describes the problem, the root cause analysis, and the corrective actions.